Surveyors and structural engineers utilise data from tables below to help calculate the correct size strength and centres of roof timbers for the required spans and loadings.
Flat roof timber span tables.
They also tell you what the maximum spacing should be between each section or timber member size of joists mm clear span c16 joist m clear span c24 joist m 47 x 95 47 x 120 47 x 145 47 x 170 47 x 195 47 x 220 1 77 2 40.
For pitched roofs flat roofs and ceiling joists.
Surveyors span tables for designing roof rafters.
These span tables apply only to flat roof and roof with a slope of up to 10 degrees.
Joist and rafter span tables.
Notches are not to exceed 0 125 of the depth of the joist and are to be located between 0 07 and 0 25 of the span from the support.
For simple construction such as domestic construction this can be determined from span table supplements in as1684 2 and as1684 3.
R cb150 16 beam span table used w 3600 width of frame rafter span χ 6410 fascia beam span the cb150 16 beam achieves the 6000mm span for the fascia beam and can be used for the rafters.
View joist rafter tables.
Span tables span tables can be used to determine the size of a timber member of a particular strength class required for a given span.
Timber to be covered these span tables do not apply to timber which is fully exposed to the elements.
View size selection tables.
Stress grades and timber sizes combine to determine the spanning ability of load carrying members.
Attached flat roof 1ao page14.
Span tables use the span tables below to determine allowable lengths of joists and rafters based on size and standard design loads.
You can also use the wood beam calculator from the american wood council website to determine maximum rafter and joist lengths.
Listed are 46 tables based on common loading conditions for floor joists ceiling joists and rafters.
Span tables for ceiling joists to bs 5268 7 3 span tables for flat roof joists to bs 5268 7 2 imposed loads of 0 75 kn m for maintenance and snow load are applicable where there is no permanent access no fixed ladder or staircase and most areas where the altitude does not exceed 100 metres refer to bs 6399 3.
Span tables allow users to choose an appropriate size and stress grade to achieve spanning needs.
